Magnetotransport in Ferromagnetic (Ga, Mn)As and (Ga, Mn)N Pn-Diodes

GaAs and GaN pn-junctions are fabricated with Mn-doped ferromagnetic layers on top of nonmagnetic substrates. In the case of heavily doped (Ga,Mn)As/GaAs p
⁺⁺
n
⁺⁺
-junctions (Zener diodes) the tunneling current becomes magnetic field dependent at low temperatures. This can be explained by a model based on the valence band splitting due to the exchange interaction between the hole spins and the localized spins of the Mn atoms. In the pn-junctions with more lightly doped nonmagnetic regions in the (Ga, Mn)N and (Ga, Mn)As diodes, no magnetic field dependence in the I-V characteristics is observed, probably due the absence of ferromagnetism in the depletion region of the p
⁺
n-junctions